drm/amd/display: Fix DML dummyinteger types mismatch

[Why]
The types for dummyinteger1 and dummyinteger2 are unsigned
as part of the DML spec. They should not be long.

[How]
Make them unsigned int instead of long.

Signed-off-by: Jerry (Fangzhi) Zuo <Jerry.Zuo@amd.com>
Reviewed-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>